In heterogeneous nuclear reactors, the used fuel elements have to be replaced or rearranged in the reactor core after predetermined time intervals. In water reactors, such a fuel element exchange may be effected in two ways: In case of a so-called "dry" exchange, the fuel element is drawn under water into a closable steel container and the latter is, together with the enclosed cooling water and the fuel element, transported into a fuel element storage pool. In case of a so-called "wet" fuel element exchange, the reactor pool and the adjacent fuel element storage pool are interconnected by means of a channel in which there is disposed a watertight gate. As a preparatory step to the wet fuel element exchange, the water level in the reactor pool is raised to the water level in the fuel element storage pool and the gate is opened. Subsequently, the fuel elements may be grasped with specially designed tools mounted on a travelling fuel element exchange gantry and moved through the connecting channel between the reactor and the assigned storage space in the fuel element storage pool. In case the fuel elements are disposed in sheaths (boxes), a conventional box-stripping machine has to be provided in addition.
The invention relates to a system for performing a wet fuel element exchange process. Heretofore, for effecting this type of exchange, the rails on which the gantry travels have been disposed at the same height as the edge of the fuel element storage pool and the level of the operating platform. Further, the box-stripping machines and tool storing devices have been disposed in the rear part of the fuel element storage pool which requires that these apparatuses project beyond the pool edge.
It is a disadvantage of the above-outlined known systems for effecting a wet fuel element exchange that they involve long travelling paths and thus require long periods of reactor shutdowns.